Motor having a plain bearing for adjusting an axial play of a rotor shaft and associated method therefor

ABSTRACT

In order to simplify the adjustment of an axial play of a rotor shaft ( 2.4 ) between the rotor shaft ( 2.4 ) and a stator ( 1 ) of a motor with the purpose of reducing the component expenditure and the assembly expenditure of the motor, respective clamp holders ( 3; 4 ) exert pressure on both sides of a plain bearing ( 5 ). These clamp holders ( 3; 4 ) are axially moved to respective operating end positions in a bearing receiver ( 1. 1; 7.1 ). There, the clamp holders ( 3; 4 ), which have different spring stiffness, are fixed by respective claws. The clamp holder ( 3 ) which has the higher spring stiffness adjusts the axial play of the rotor shaft ( 2.4 ) while the clamp holder ( 4 ) which has the lower spring stiffness exerts, in particular, an elastic axial pressure against the plain bearing ( 5 ) and, therefore, against the first clamp holder ( 3 ).

[0001] This is a Divisional of Application No. 09/793,960, filed Feb.28, 2001, which is a Continuation of International ApplicationPCT/DE99/02694, with an international filing date of Aug. 27, 1999,which was published under Article 21(2) in German. The disclosures ofthe Continuation and of the International Application are incorporatedinto this application by reference.

FIELD OF AND BACKGROUND OF THE INVENTION

[0002] The present invention relates to a motor having a plain bearing,especially a cup and ballbearing, for a rotor shaft whose axial play isadjusted. The invention also relates to an associated method foradjusting the axial play of the rotor shaft.

[0003] The rotor shafts of mass-produced motors, whose stators includeseveral components, may have an impermissible axial play. The axial playmay be too high due to tolerances of the individual components of themotor. Therefore, when the motor is assembled, there is a need in theart to adjust this axial play of the rotor shaft to a pre-definedpermissible range.

[0004] European Patent Application EP 0 592 303 A1 discloses a motor,which has a cup and ballbearing. The cup and ballbearing can be adjustedaxially in a bearing receiver by means of a single clamp holder. In itsoperating end position, the cup and ballbearing can be fixed by a claw.To do this, the single clamp has two types of radial fingers distributedaround its circumference. Specifically, fingers that are bent inward tohold the plain bearing in an embracing manner alternate with fingershaving claw ends that project radially outward to fix the clamp in thebearing receiver.

[0005] U.S. Pat. No. 3,770,990 teaches a bearing arrangement for ashaft. A spherical cap is mounted on each end of the shaft. Each of thespherical caps, which contact respective clamp holders, is divided intwo axial parts. Together with the shaft, one of the parts of arespective spherical cap can be rotated relative to the other, restingpart in order to compensate for any radial play.

[0006] German Patent DD 259 504 A1 teaches a fastening for plainbearings that compensates axle displacements, wherein the plain bearingsare located in plastic end shields. In this method, a pendulum plainbearing is, on one of its axial face sides, fixed in axial direction bymeans of a pressure disk that is held in a bearing shaft. At its otheraxial face side, the pendulum plain bearing is pressed, with elasticstress, against a spherical ring surface of the end shield.

OBJECTS OF THE INVENTION

[0007] It is one object of the present invention to provide a simpleradjustment of an axial play of rotor shafts of mass-produced motors inorder to reduce the expenditure for manufacturing and assembling thesemotors. A further object is to provide a simple adjustment for motors inwhich the respective rotor shaft is rotatably borne in a plain bearing,in particular a cup and ballbearing, while an optimal damping of axialvibrations of the rotor and an operationally safe adjustment of theplain bearing is ensured. While the present invention is not limited toa specific type of plain bearing, it is another object that thesimplified adjustment is suitable if the plain bearing is embodied as aspherical cap, for example.

SUMMARY OF THE INVENTION

[0008] According to one formulation of the present invention, these andother objects are achieved by a motor which has a plain bearing toadjust an axial play of a rotor shaft of the motor. The motor includes astator; a first clamp holder which is arranged at one axial face side ofthe plain bearing; and a second clamp holder which is arranged at theother axial face side of the plain bearing. Therein, the springstiffness of the first clamp holder is higher than the spring stiffnessof the second clamp holder. A bearing receiver receives the first clampholder, the second clamp holder, and the plain bearing. The first clampholder and the second clamp holder are, independently of each other,moved to a respective operating end position in the bearing receiver,where they are fixed. Therein, the first clamp holder contacts the oneaxial face side of the plain bearing in order to adjust the axial playbetween the rotor shaft and the stator of the motor, wherein the rotorshaft is borne in the plain bearing. The second clamp holder contactsthe other axial face side of the plain bearing in order to exert anelastic pressure against the plain bearing and against the first clampholder.

[0009] According to another formulation of the present invention, theseand other objects are achieved by a method for adjusting an axial playof a rotor shaft of a motor. In a first step of the method according tothe present invention, the rotor of the motor is positioned relative tothe motor housing. In a second step, the bearing receiver is fixedrelative to the motor housing in that, at the axially inner end of thebearing receiver, the second clamp holder is inserted in the bearingreceiver and moved to a second operating end position, where the secondclamp holder is fixed. At the axially outer end of the bearing receiver,the plain bearing and the first clamp holder are axially inserted intothe bearing receiver. The first clamp holder is moved to a firstoperating end position in order to adjust a pre-defined axial play ofthe rotor shaft. At the first operation end position, the first clampholder is fixed.

[0010] Using very simple, standard clamps, the motor according to theinvention permits a simple adjustment of the axial play of the rotorshaft of the motor. The axial play adjustment is carried out by axiallydisplacing the first clamp holder when the motor is assembled. Thereby,an adjustment over even long axial adjusting paths is achieved. At thesame time, an optimal damping of axial vibrations is ensured. Due to theprovision of the second, easily-to-install clamp holder, whose springcharacteristic is designed independently of the first clamp holder, thedanger of a loose plain bearing is avoided. The plain bearing can be aspherical cap, for example. In a particularly simple manner in terms ofmanufacturing the clamp holders, each clamp holder includes a clamp thathas a radially outer, closed clamping edge. Furthermore, fingers, whichproject inwardly from the clamping edge, touch the plain bearing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The invention and further advantageous refinements of theinvention according to the features of the dependent claims areexplained in more detail below with the aid of diagrammatic, exemplaryembodiments in the drawings, in which:

[0012]FIG. 1 is an axial cross section of a commutator motor having abearing receiver which is held at the right axial end of the motorhousing via an end shield, wherein the bearing receiver includes clampholders according to the present invention for a plain bearing, inparticular a spherical cup and ballbearing;

[0013]FIG. 2 is an arrangement according to FIG. 1, in which the bearingreceiver is part of an adapter receiving the motor housing;

[0014]FIG. 3 is an axial top view toward a first clamp holder having ahigh spring stiffness;

[0015]FIG. 4 is a rotor-side axial top view of a second clamp holderhaving a low spring stiffness; and

[0016]FIG. 5 is an axial cross-sectional view of the two clamp holdersaccording to FIGS. 3;4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017]FIG. 1 shows an axial cross section of a commutator motor that isexcited by a permanent magnet. Such a motor is used, for example, todrive fans in motor vehicles. On the inner circumference of a motorhousing 1.3, a stator 1 has magnetic shells 1.4 to permanently excitethe commutator motor.

[0018] In addition, the stator 1 has bearing receivers 1.1; 1.2 that aremounted on respective axial ends of the motor housing 1.3.

[0019] A rotor 2 includes a rotor package 2.1, which is held on a rotorshaft 2.4. A winding 2.2 is connected to a commutator 2.3, which isbrushed by I10 brushes that are not shown. The rotor shaft 2.4 isrotatably borne in a right plain bearing 5 on an AS side of the motorand in a left plain bearing 6 on a BS side of the motor. The plainbearings 5, 6 can be spherical caps, for example. In a conventionalmanner, one axial end of the left spherical cap is pressed against thefixed bearing receiver 1.2 by a clamp 11. Preferably, the fixed bearingreceiver 1.2 is embodied in a ball socket shape.

[0020] According to the invention, the right spherical cap 5 is held inthe bearing receiver 1.1 by a first clamp holder 3, which is arranged orsurface-mounted in the area of the right axial end of the rightspherical cap, and by a second clamp holder 4, which is arranged orsurface-mounted in the area of the left axial end of the right sphericalcap 5. Preferably, the bearing receiver 1.1 has a cylindrical form inthis area. The spherical cap 5 is held in the bearing receiver 1.1 insuch a way that the right spherical cap 5 can be axially adjusted. Alubricant deposit reservoir 10 is provided between the first clampholder 3 and the second clamp holder 4 to lubricate the contact areabetween the spherical cap 5 on the one hand and the first clamp holder 3and the second clamp holder 4 on the other.

[0021] The two clamp holders 3 and 4 have different springcharacteristics. The first clamp holder 3, which is arranged at theaxially outer side, has a steep spring characteristic curve. The secondclamp holder, which is arranged at the axially inner side, has a flatterspring characteristic curve. The different spring characteristics aredetermined by the number and the design of radially inner fingers, whichare preferably formed on respective radially outer clamping edges 3.1;4.1 of the clamp holders 3; 4, as shown in FIGS. 3 and 4. Since theclamp holder 3 has a relatively high stiffness, the clamp holder 3 shownin FIG. 3 has only a few, e.g. three, fingers 3.2 and/or the finger areathat is radially inside relative to the outer clamping edge 3.1 has onlyshort slits. As shown in FIG. 4, the second clamp holder 4, has, inaccordance with its relatively soft spring characteristic, a total often narrower fingers 4.2, which are formed from the single-piece clampby greater and deeper slits.

[0022] The desired range for the axial play is determined by the depthof the axial insertion of the right first clamp holder 3 into thebearing receiver 1.1. This range for the axial play is defined, forexample, by an axial contact path between the left front face of theplain bearing 5 and the opposing front face 8.1 of an isolating end disk8, which is fastened to the rotor package. When the spherical cap 5 ismoved axially to adjust the axial play of the rotor shaft 2.4 by meansof the first clamp holder 3, the fingers 4.2 of the left second clampholder 4 yield in a more or less resilient manner. Therein, the secondclamp holder 4 has a flat spring characteristic curve. At the same time,the left second clamp holder 4 remains fixed in its pre-assembled andadjusted axial position. Advantageously, the relatively flat springcharacteristic of the inner second clamp holder 4 is used, among otherthings, to ensure that the spherical cap 5 is received in the bearingreceiver 1.1 in such a way that the spherical cap 5 is secured againstturning. By the same token, the relatively flat spring characteristicmakes the second holder 4 soft enough to permit the spherical cap 5,which is received in the bearing receiver 1.1, to be adjusted in orderto compensate misalignments.

[0023] In the operating end position of the spherical cap 5, thespherical cap 5 is pressed against the axially outer first clamp holder3 by the resilient fingers 4.2 of the axially inner second clamp holder4. Since the first clamp holder 3 has a steep spring characteristiccurve, the fingers 3.2 of first clamp holder 3 practically do not yieldin the axial direction. Thus, the spring characteristic curve of theaxially inner second clamp holder 4 is not adequate to push the axiallyouter first clamp holder 3 back. Preferably, the spring characteristiccurve of the outer first clamp holder 3 is designed in such a way thatit can damp axial strains of the rotor shaft, just like the axial innersecond clamp holder 4 does in the opposite direction. These axialstrains are due to strong magnetic axial tension and/or due to strongaxial mechanical shock, for example.

[0024] Preferably, in order to achieve an especially simple axial playadjustment by means of the two clamp holders 3; 4, which have differentspring characteristic curves, the axially inner second clamp holder 4 ispre-assembled at an operating end position in the bearing receiver 1.1.After the bearing receiver 1.1 is attached to the stator 1, which hasthe rotor already mounted in the stator bore, the spherical cap 5 andthe axially outer first clamp holder 3 are inserted into the bearingreceiver 1.1. Thereafter, the spherical cap 5 and the axially outerfirst clamp holder 3 are moved to their respective operating endpositions in order to adjust a pre-defined axial play of the rotor shaft2.4.

[0025] In addition to the pre-assembled axially inner second clampholder 4, the spherical cap and the axially outer first clamp holder 3are, according to another preferred embodiment of the invention,pre-assembled in the bearing receiver 1.1 too. After fastening thebearing receiver 1.1 at the stator 1 (wherein the rotor 2 was previouslypositioned in the bearing bore of the stator 1), the spherical cap 5 andthe axial outer first clamp holder 3 are further pressed into thebearing receiver 1.1 to adjust the pre-defined axial play of the rotorshaft 2.4.

[0026] Advantageously, when the clamp holders 3; 4 reach their operatingend positions, the clamp holders 3; 4 are fastened in the bearingreceiver 1.1 via their respective clamp edges 3.1; 4.1. Preferably, theclamp holders 3; 4 are automatically fastened by means of respectiveclaws. For this purpose, the clamping edges 3.1; 4.1 point in adirection opposite to the insertion direction in order to form therespective claws, as shown in the cross section of FIG. 5.

[0027] In the preferred embodiment shown in FIG. 2, a bearing receiver7.1, which receives the spherical cap 5 and the clamp holders 3; 4, isan integral part of an adapter 7, which receives the motor in anembracing manner. This preferred embodiment is particularly advantageousfor pre-assembling the clamp holders 3; 4 according to the presentinvention. By means of the adapter 7, the motor can be easily installedin a holder, such as a holder of a motor fan assembly in a motorvehicle.

[0028] The clamp holders 3; 4 according to the present invention, whichare, in the preferred embodiments discussed above, provided on the ASend of the rotor shaft 2.4 can, of course, also or instead be providedon the BS end of the rotor shaft 2.4.

[0029] The above description of the preferred embodiments has been givenby way of example. From the disclosure given, those skilled in the artwill not only understand the present invention and its attendantadvantages, but will also find apparent various changes andmodifications to the structures and methods disclosed. It is sought,therefore, to cover all such changes and modifications as fall withinthe spirit and scope of the invention, as defined by the appendedclaims, and equivalents thereof.

What is claimed is:
 1. A method for adjusting an axial play of a rotorshaft of a motor with a first and a second clamp holder, comprising: (a)positioning a rotor of the motor relative to a housing of the motor; (b)fixing a bearing receiver relative to the housing of the motor byinserting, at an axially inner end of the bearing receiver, the secondclamp holder; by moving the second clamp holder to a second operatingend position; and by fixing the second clamp holder at the secondoperating end position; (c) at an axially outer end of the bearingreceiver, axially inserting a plain bearing into the bearing receiver;(d) at the axially outer end of the bearing receiver, axially insertingthe first clamp holder into the bearing receiver; (e) moving the firstclamp holder to a first operating end position to adjust a pre-definedaxial play of the rotor shaft; and (f) fixing the first clamp holder atthe first operating end position.
 2. A method for adjusting an axialplay of a rotor shaft of a motor with a first and a second clamp holder,comprising: (a) positioning a rotor of the motor relative to a housingof the motor; (b) fixing a bearing receiver relative to the housing ofthe motor by inserting, at an axially inner end of the bearing receiver,the second clamp holder; by moving the second clamp holder to a secondoperating end position; by fixing the second clamp holder at the secondoperating end position; by axially inserting, at an axially outer end ofthe bearing receiver, a plain bearing into the bearing receiver; byinserting, at the axially outer end of the bearing receiver, the firstclamp holder into the bearing receiver; and by moving the first clampholder to a pre-assembly position; (c) moving the first clamp holderaxially to a first operating end position to adjust a pre-defined axialplay of the rotor shaft; and (d) fixing the first clamp holder at thefirst operating end position.
 3. The method of claim 2, comprising:placing the first clamp holder against the plain bearing withoutexerting significant axial pressure; and placing the second clamp holderagainst the plain bearing in a resilient and operationally safe mannerso that the second clamp holder presses against the first clamp holder.